Fuel cell motor vehicle and method

ABSTRACT

A fuel cell vehicle includes a fuel cell assembly with at least a first fuel cell stack and a second fuel cell stack. Waste gas extracted from the first fuel cell stack is routed to an input of the second fuel cell stack. The first and second fuel cell stacks may be of the same size or the second fuel cell stack may be sized smaller than the first fuel cell stack.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims foreign priority benefits under 35 U.S.C. §119(a)-(d) to DE Application 10 2020 214 166.5 filed Nov. 11, 2020,which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

This disclosure relates to a fuel cell motor vehicle and method.

BACKGROUND

In a fuel cell motor vehicle, electrical energy is generated by a fuelcell from hydrogen or methanol as energy sources and is converteddirectly into kinetic energy by the electric drive or temporarily storedin a traction battery.

US 2005/0064269 A1 and WO 2020/018832 A1 each disclose fuel cellassemblies having at least one fuel cell stack.

Fuel cells are operated with a stoichiometric ratio greater than 1, i.e.with an excess of reactants, leading to a nonoptimal utilization of thefed in reactants. Such fuel cell stacks are limited in terms of theirpower. For higher power outputs, a plurality of fuel cell stacks must becombined in a fuel cell assembly. In addition to the fuel cell stacks,however, this requires the provision of more powerful or additionalcomponents (balance of plant—BOP), in particular compressors and/orhumidifiers, which are required for operation of the fuel cell stacks.

SUMMARY

A fuel cell vehicle and a method fur operating a fuel cell vehiclehaving a fuel cell assembly with at least one first fuel cell stack andone second fuel cell stack include extracting waste gas from the firstfuel cell stack and feeding the extracted waste gas to the second fuelcell stack.

The second fuel cell stack is thus at least partially and/or temporarilysupplied with waste gas from the first fuel cell stack. This makes itpossible to dimension a compressor and a humidifier which are assignedto the second fuel cell stack to be smaller than the compressor and thehumidifier which are assigned to the first fuel cell stack.

According to one embodiment, the first fuel cell stack and the secondfuel cell stack are of the same size, It is thus possible to useidentical components for the two fuel cell stacks. This also enables thefirst fuel cell stack and the second fuel cell stack to be operatedindependently of one another.

According to a further embodiment, a compressor and/or humidifierassigned to the second fuel cell stack are/is of smaller dimensions thanthe compressor and/or humidifier assigned to the first fuel cell stack.It is thus possible to use components with a lower installation spacerequirement and/or a lower energy requirement, This also enables thefirst fuel cell stack and the second fuel cell stack to be operatedindependently of one another.

According to a further embodiment, the extracted waste gas is fed on theinlet side to a compressor assigned to the second fuel cell stack. Forthis purpose, a valve is arranged between an outlet of the first fuelcell stack and an inlet of the second fuel cell stack, by means of whichvalve a line connecting this inlet and outlet can be opened. It is thusa particularly simple matter to supply the second fuel cell stack atleast partially and/or temporarily with waste gas from the first fuelcell stack. This also enables the first fuel cell stack and the secondfuel cell stack to be operated independently of one another.

According to a further embodiment, a pressure distribution valve isprovided on the outlet side on a compressor assigned to the first fuelcell stack. With the pressure distribution valve, both the first fuelcell stack and the second fuel cell stack can be supplied with air oroxygen at a respective pressure. This also enables the first fuel cellstack and the second fuel cell stack to be operated independently of oneanother.

According to a further embodiment, a compressor which is assigned to thefirst fuel cell stack and has two pressure outlets is provided. Thus,only a single compressor is necessary, reducing the number of componentsrequired. Flow distribution is achieved by means of two throttle valves,which are assigned on the input side to the respective humidifier of therespective fuel cell stack. This also enables the first fuel cell stackand the second fuel cell stack to be operated independently of oneanother.

According to a further embodiment, the first fuel cell stack and thesecond fuel cell stack are of different sizes. This allows both fuelcell stacks to be operated with just a single compressor and just asingle humidifier. However, this does not enable the first fuel cellstack and the second fuel cell stack to be operated independently of oneanother.

According to a further embodiment, the extracted waste gas is fed to thesecond fuel cell stack via a valve. For this purpose, a valve isarranged between an outlet of the first fuel cell stack and an inlet ofthe second fuel cell stack, by means of which valve a line connectingthis inlet and outlet can be opened. It is thus a particularly simplematter to supply the second fuel cell stack at least partially and/ortemporarily with waste gas from the first fuel cell stack. However, thisdoes not enable the first fuel cell stack and the second fuel cell stackto be operated independently of one another.

According to a further embodiment, humidified air or oxygen can be fedto the first fuel cell stack and/or to the second fuel cell stack via afurther valve. For this purpose, a further valve is provided, whichenables the second fuel cell stack to be supplied directly withcompressed air. Furthermore, this enables waste gas from the second fuelcell stack to be passed together with waste gas from the first fuel cellstack through a humidifier which is assigned to the first fuel cellstack. This also enables the first fuel cell stack and the second fuelcell stack to be operated independently of one another.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic representation of one embodiment of a fuel cellassembly for a fuel cell motor vehicle.

FIG. 2 shows, in schematic representation, another embodiment of a fuelcell assembly for a fuel cell motor vehicle,

FIG. 3 shows, in schematic representation, another embodiment of a fuelcell assembly for a fuel cell motor vehicle,

FIG. 4 shows, in schematic representation, another embodiment of a fuelcell assembly for a fuel cell motor vehicle,

FIG. 5 shows, in schematic representation, another embodiment of a fuelcell assembly for a fuel cell motor vehicle, and

FIG. 6 shows, in schematic representation, another embodiment of a fuelcell assembly for a fuel cell motor vehicle.

DETAILED DESCRIPTION

Detailed embodiments of the present invention are disclosed herein.However, it is to be understood that the disclosed embodiments aremerely examples of the claimed subject matter and may be embodied invarious and alternative forms. The figures are not necessarily to scale;some features may be exaggerated or minimized to show details ofparticular components. Therefore, specific structural and functionaldetails disclosed herein are not to be interpreted as limiting, butmerely as a representative basis for teaching one skilled in the art tovariously employ the claimed subject matter.

As shown in the representative embodiment of FIG. 1, a fuel cellassembly 4 for a fuel cell motor vehicle 2 has a first fuel cell stack 6a and a second fuel cell stack 6 b for this purpose. Those of ordinaryskill in the art will recognize that the fuel cell assembly 4 can alsohave further fuel cell stacks. The first fuel cell stack 6 a and thesecond fuel cell stack 6 b are of the same size.

Further illustrated components in the balance of plant (BOP) of the fuelcell assembly 4 include two compressors 8 a, 8 b, two humidifiers 10 a,10 b, two filters 20 a, 20 b, two coolers 22 a, 22 b, which arewater-cooled in the embodiment illustrated, in each case two valves 24,26 and 28, 30, two throttle valves 32 a, 32 b and two hydrogen purgevalves 34 a, 34 b.

In addition or as an alternative to the throttle valves 32 a, 32 b,turbines can also be provided. In this arrangement, one of thecomponents is assigned to each of the two fuel cell stacks 6 a, 6 b. Inother words, the first fuel cell stack 6 a. has a compressor 8 a,humidifier 10 a, etc., assigned to it. Likewise, the second fuel cellstack 6 b has a compressor 8 b, humidifier 10 b, etc., assigned to it.

During operation, air or oxygen is fed to the first fuel cell stack 6 ain its flow direction via the filter 20 a, the compressor 8 a and thewater-cooled cooler 22 a and the humidifier 10 a. Air or oxygen whichhas flowed through the first fuel cell stack 6 a is passed through thehumidifier 10 a, wherein a throttle valve 32 a is arranged downstream ofthe humidifier 10 a for control purposes. By means of a valve 24, it ispossible to open a first bypass 36, with which the humidifier 10 a, thefirst fuel cell stack 6 a and the throttle valve 32 a can be bypassed.

By means of a valve 26, which in the embodiment of FIG. 1 is arrangeddownstream of the valve 24, it is possible to open a second bypass 38,with which the humidifier 10 a can be bypassed. To purge the first fuelcell stack 6 a, a hydrogen purge valve 34 a is provided, by means ofwhich a connection to an outlet 16 can be established.

Similarly, air or oxygen is fed to the second fuel cell stack 6 b in itsflow direction via the filter 20 b, the compressor 8 b and thewater-cooled cooler 22 b and the humidifier lob. Here too, air or oxygenthat has flowed through the second fuel cell stack 6 b is passed throughthe humidifier 10 b, wherein a throttle valve 32 b is arrangeddownstream of the humidifier lob for control purposes.

By means of a further valve 28, air or oxygen which has flowed throughthe water-cooled cooler 22 b, or the waste gas from the first fuel cellstack 6 a, can be fed to the second fuel cell stack 6 b or a connectionto the outlet 16 can be established. By means of a further valve 30arranged downstream of the valve 28, it is possible to open a thirdbypass 40, with which the humidifier 10 b can be bypassed. To purge thesecond fuel cell stack, 6 b, a hydrogen purge valve 34 b is provided, bymeans of which a connection to the outlet 16 can be established.

The first bypass 36 extends from the valve 24 to the further valve 28,i.e. in the embodiment of FIG. 1, it opens downstream of thewater-cooled cooler 22 b into a supply line which connects the filter 20b, the compressor 8 b and the water-cooled cooler 22 b.

During operation, in a first step, waste gas from the first fuel cellstack 6 a can be extracted, and in a second step, the extracted wastegas can be fed to the second fuel cell stack 6 b. The extracted wastegas flows through the humidifier 10 a, the throttle valve 32 a, and thefurther valves 28, 30, and is then passed via the humidifier lob and/ordirectly into the second fuel cell stack 6 b. The second fuel cell stack6 b is thus at least partially and/or temporarily supplied with wastegas from the first fuel cell stack 6 a. This makes it possible todimension the compressor 8 b and the humidifier 10 b which are assignedto the second fuel cell stack 6 b to be smaller than the compressor 8 aand the humidifier 10 a which are assigned to the first fuel cell stack6 a. Furthermore, the arrangement illustrated in FIG. 1 enables thefirst fuel cell stack 6 a and the second fuel cell stack 6 b to beoperated independently of one another.

The embodiment illustrated in FIG. 2 differs from the embodimentillustrated in FIG. 1 in that the first bypass 36 opens downstream ofthe filter 20 a and upstream of the compressor 8 a into the supply linewhich connects the filter 20 b, the compressor 8 b and the water-cooledcooler 22 b. The extracted waste gas flows through the humidifier 10 a,the throttle valve 32 a, the compressor 8 b, the water-cooled cooler 22b, and the further valves 28, 30, and is then passed via. the humidifier10 b and/or directly into the second fuel cell stack 6 b. The secondfuel cell stack 6 b is thus at least partially and/or temporarilysupplied with waste gas from the first fuel cell stack 6 a. This toomakes it possible to dimension the compressor 8 b and the humidifier lobwhich are assigned to the second fuel cell stack 6 b to be smaller thanthe compressor 8 a and the humidifier 10 a which are assigned to thefirst fuel cell stack 6 a. Furthermore, the arrangement illustrated inFIG. 2 enables the first fuel cell stack 6 a and the second fuel cellstack 6 b to be operated independently of one another.

The embodiment illustrated in FIG. 3 differs from the embodimentillustrated in FIG. 1 in that only one filter 20 a and one compressor 8a are provided for supplying the two fuel cell stacks 6 a and 6 b.Downstream of the compressor 8 a, a pressure distribution valve 12having a first outlet and a second outlet is provided, wherein the firstoutlet is connected to the water-cooled cooler 22 a and the secondoutlet is connected to the water-cooled cooler 22 b. Similar to theembodiment of FIG. 1, the extracted waste gas flows through thehumidifier 10 a, the throttle valve 32 a, and the further valves 28, 30,and is then passed via the humidifier 10 b and/or directly into thesecond fuel cell stack 6 b. The second fuel cell stack 6h is thus atleast partially and/or temporarily supplied with waste gas from thefirst fuel cell stack 6 a, and only a single compressor 8 a is required.

The embodiment illustrated in FIG. 4 differs from the embodimentillustrated in FIG. 3 in that, instead of the pressure distributionvalve 12 of FIG. 3, a compressor 8 a which has two pressure outlets,each of the outlets being assigned a throttle valve 14 a, 14 b isprovided in FIG. 4. The second fuel cell stack 6 b is thus at leastpartially and/or temporarily supplied with waste gas from the first fuelcell stack 6 a, and likewise only one compressor 8 a is required.

The embodiment illustrated in FIG. 5 differs from the embodimentsillustrated in FIGS. 1 to 4 in that the first fuel cell stack 6 a andthe second fuel cell stack 6 b are of different sizes. The first fuelcell stack 6 a is larger than the second fuel cell stack 6 b. Theembodiment illustrated in FIG. 5 furthermore differs from theembodiments illustrated in FIGS. 1 and 2 in that only a single filter 20a and a single compressor 8 a as well as just one humidifier 10 a areprovided for supplying the two fuel cell stacks 6 a and 6 b. Theextracted waste gas flows through the humidifier 10 a, the throttlevalve 32 a, and the further valve 28 directly into the second fuel cellstack 6 b. The arrangement illustrated in FIG. 5 does not enable thefirst fuel cell stack 6 a and the second fuel cell stack 6 b to beoperated independently of one another.

The embodiment illustrated in FIG. 6 differs from the embodimentillustrated in FIG. 5 in that the valve 30 is used to open a furtherbypass 42, which enables the second fuel cell stack 6 b to be supplieddirectly with compressed air, which is provided by the compressor 8 a.Furthermore, this enables waste gas from the second fuel cell stack 6 bto be passed together with waste gas from the first fuel cell stack 6 athrough a humidifier 10 a which is assigned to the first fuel cell stack6 a. Thus, the bypass 42 returns humid waste gas from the second fuelcell stack 6 b to the humidifier 10 a in order to humidify the inlet airif this is necessary. Furthermore, a further line 18 can be used tosupply the second fuel cell stack ob with fresh air. Via the line 42,humid waste gas can he returned from the second fuel cell stack 6 b tothe humidifier 10 a. This arrangement enables the first fuel cell stack6 a and the second fuel cell stack 6 b to be operated independently ofone another. The pressure can he controlled by means of the throttlevalve 32 a. The extracted waste gas flows through the humidifier 10 a,the throttle valve 32 a, the water-cooled cooler 32 a and the furthervalve 28 into the second fuel cell stack 6 b. The arrangementillustrated in FIG. 6 enables the first fuel cell stack 6 a and thesecond fuel cell stack 6 b to be operated independently of one another.

With arrangements according to representative embodiments as describedabove, it is possible to provide a fuel cell assembly 4 which requiresapproximately 20% less operating energy, for example.

While representative embodiments are described above, it is not intendedthat these embodiments describe all possible forms of the claimedsubject matter. The words used in the specification are words ofdescription rather than limitation, and it is understood that variouschanges may be made without departing from the teachings of thedisclosure and the claimed subject matter. Additionally, the features ofvarious implementing embodiments may be combined to form furtherembodiments of the invention.

What is claimed is:
 1. A method for operating a fuel cell vehicle havinga fuel cell assembly with at least a first fuel cell stack and a secondfuel cell stack, the method comprising: extracting waste gas from thefirst fuel cell stack; and routing the extracted waste gas to an inputof the second fuel cell stack.
 2. The method according to claim 1,wherein the first fuel cell stack and the second fuel cell stack are thesame size.
 3. The method according to claim 2, wherein a compressorupstream of the second fuel cell stack is of smaller dimensions than acompressor upstream of the first fuel cell stack.
 4. The methodaccording to claim
 3. further comprising feeding the waste gas extractedfrom the first fuel cell stack to an inlet side of the compressorupstream of the second fuel cell stack.
 5. The method according to claim3, further comprising routing gas from an outlet of the compressorupstream of the first fuel cell stack through a pressure distributionvalve.
 6. The method according to claim 3, wherein the compressorupstream of the first fuel cell stack has two pressure outlets.
 7. Afuel cell system comprising: a first fuel cell stack: a second fuel cellstack; a first compressor disposed upstream of the first fuel cell stackand having an outlet coupled to an inlet of the first fuel cell stack;and a throttle valve operable to route waste gas from the first fuelcell stack to an input of the second fuel cell stack.
 8. The fuel cellsystem of claim 7 further comprising: a second compressor disposedupstream of the second fuel cell stack and having an outlet coupled toan inlet of the second fuel cell stack.
 9. The fuel cell system of claim8 wherein the throttle valve is operable to route waste gas from thefirst fuel cell stack to an input of the second compressor.
 10. The fuelcell system of claim 8 wherein the throttle valve is operable to routewaste gas from the first fuel cell stack to the output of the secondcompressor.
 11. The fuel cell system of claim 7 wherein the outlet ofthe first compressor is coupled to the inlet of the second fuel cellstack.
 12. The fuel cell system of claim 11 further comprising apressure distribution valve having an inlet coupled to the outlet of thefirst compressor, a first outlet coupled to the inlet of the first fuelcell stack, and a second outlet coupled to the inlet of the second fuelcell stack.
 13. The fuel cell system of claim 7 wherein the firstcompressor comprises a second outlet and wherein the second outlet iscoupled to the inlet of the second fuel cell stack.
 14. The fuel cellsystem of claim 7 further comprising a humidifier disposed between thecompressor and the first fuel cell stack, the humidifier configured totransfer water vapor between the waste gas of the first fuel cell stackand the inlet of the first fuel cell stack.
 15. The fuel cell system ofclaim 14 further comprising a second humidifier configured to transferwater vapor between the waste gas of the second fuel cell stack and theinlet of the second fuel cell stack.
 16. The fuel cell system of claim14 wherein an outlet of the second fuel cell stack is coupled to thehumidifier and wherein the humidifier is configured to transfer watervapor between the waste gas of the second fuel cell stack and the inletof the second fuel cell stack.
 17. A fuel cell vehicle comprising: afirst fuel cell stack; a second fuel cell stack; a compressor; ahumidifier having an inlet coupled to an outlet of the compressor, theoutlet of the humidifier coupled to an input of at least one of thefirst and second fuel cell stacks; and a throttle valve coupled to anoutlet of the first fuel cell stack and the input of the second fuelcell stack and configured to direct waste gas from the first fuel cellstack to the input of the second fuel cell stack.
 18. The fuel cellvehicle of claim 17 further comprising: a second compressor; and asecond humidifier having an inlet coupled to an outlet of the secondcompressor, the outlet of the second humidifier coupled to the input ofthe second fuel cell stack.
 19. The fuel cell vehicle of claim 17further comprising: a second humidifier having an inlet coupled to asecond outlet of the compressor and an outlet coupled to the input ofthe second fuel cell stack.
 20. The fuel cell vehicle of claim 17wherein the first and second fuel cell stacks are the same size.